Gyros have been used to measure rotation rates or changes in angular velocity about an axis of rotation. A basic conventional fiber optic gyro (FOG) includes a light source, a beam splitting device, and a fiber sensing coil coupled to the beam splitting device that encircles an area. The beam splitting device may be an integrated optics chip (IOC) that splits light from the source into beams that counter-propagate through the fiber sensing coil. The two counter-propagating beams experience different pathlengths while propagating around a rotating closed optical path, and the difference in the two pathlengths is proportional to the rotational rate that is normal to the enclosed area.
High-performance FOGs, such as may be used for submarine navigation and space-based pointing applications, typically use a gyro with very low angle random walk (ARW). ARW refers to a noise component (e.g., a drift) of the FOG output. In high-performance FOGs, ARW is predominately affected by a relative intensity noise (RIN) which results from the random intensity fluctuations of the light used for sensing rotation. RIN subtraction may be used with the FOG to reduce RIN. For example, light from the source is split into two paths at a coupler. One path directs light from the source to the IOC where the light is split into two beams, which counter-propagate through the fiber sensing coil, then recombine at the IOC and propagate back to the coupler where a portion of the light is redirected to a rate detector for rate sensing. The other path directs light from the source to a RIN detector. For an ideal gyro, the RIN at the rate and RIN detectors are a common noise that can be subtracted out. In practice, the RIN at the rate and RIN detectors may be partially de-correlated. One source of de-correlation is differential spectral filtering, which can occur because the rate and RIN optical waves propagate along different paths of the optical circuit. A spectral mismatch at the rate and RIN detectors may limit the reduction of RIN from the rate signal.
Accordingly, it is desirable to provide an optical gyro having reduced output noise. In addition, it is desirable to provide a method for determining a rotation rate of an optical gyro that reduces gyro output noise. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.